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<head><meta charset="utf-8"><title>Request for performance run · t-compiler/help · Zulip Chat Archive</title></head>
<h2>Stream: <a href="https://rust-lang.github.io/zulip_archive/stream/182449-t-compiler/help/index.html">t-compiler/help</a></h2>
<h3>Topic: <a href="https://rust-lang.github.io/zulip_archive/stream/182449-t-compiler/help/topic/Request.20for.20performance.20run.html">Request for performance run</a></h3>

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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/182449-t-compiler/help/topic/Request%20for%20performance%20run/near/210609432" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Bram van den Heuvel <a href="https://rust-lang.github.io/zulip_archive/stream/182449-t-compiler/help/topic/Request.20for.20performance.20run.html#210609432">(Sep 19 2020 at 10:56)</a>:</h4>
<p>Is someone willing to call a performance run on <a href="https://github.com/rust-lang/rust/pull/76913">#76913</a>?</p>
<blockquote>
<p>Issue <a href="https://github.com/rust-lang/rust/issues/74865">#74865</a> suggested that removing the def_id field from ParamEnv would improve performance. PR <a href="https://github.com/rust-lang/rust/issues/76244">#76244</a> implemented this change.</p>
<p>Generally, results were as expected: an instruction count decrease of about a percent. The instruction count for the unicode crates increased by about 3%, which @nnethercote speculated to be caused by a quirk of inlining or codegen. As the results were generally positive, and for chalk integration, this was also a step in the right direction, the PR was r+'d regardless.</p>
<p>However, wall-time performance results show a much larger performance degradation: 25%, as mentioned by @Mark-Simulacrum.</p>
<p>This PR, for now, reverts <a href="https://github.com/rust-lang/rust/issues/76244">#76244</a> and attempts to find out, which change caused the regression.</p>
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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/182449-t-compiler/help/topic/Request%20for%20performance%20run/near/210610644" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Joshua Nelson <a href="https://rust-lang.github.io/zulip_archive/stream/182449-t-compiler/help/topic/Request.20for.20performance.20run.html#210610644">(Sep 19 2020 at 11:33)</a>:</h4>
<p>(<span class="user-mention silent" data-user-id="216206">lcnr</span> queued a run)</p>



<a name="210611051"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/182449-t-compiler/help/topic/Request%20for%20performance%20run/near/210611051" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Bram van den Heuvel <a href="https://rust-lang.github.io/zulip_archive/stream/182449-t-compiler/help/topic/Request.20for.20performance.20run.html#210611051">(Sep 19 2020 at 11:44)</a>:</h4>
<p>I noticed, thanks <span class="user-mention" data-user-id="216206">@lcnr</span></p>



<hr><p>Last updated: Aug 07 2021 at 22:04 UTC</p>
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